1. Field of the Invention
This invention relates to an improved apparatus for increasing productivity of ice cube making machines and more specifically to an improvement in the evaporator plate in such machines.
The making of cube ice for commercial applications, such as hotels and restaurants, differs considerably from the process used in refrigerators found in the typical home. In the case of home refrigerators, trays with ice cube molds formed therein are filled with water by the consumer and placed in a section of the refrigerator, "the freezer", which is maintained at a sufficiently cold temperature to cause the water to freeze and form ice cubes. Those refrigerators with "ice makers" built in to the freezer section of the refrigerator use the same technique with the addition of a water supply line for automatically filling the ice tray, a mechanical apparatus for dumping the ice from the tray when it is formed and a timer for controlling the process.
The commercial ice cube making machines noted above use a different apparatus and methodology. These machines use a metal plate with pockets or ice cube molds in an "egg crate" or lattice structure formed on one side and refrigerant coils formed on the other side. This plate is called an evaporator plate and is formed of copper with a nickel coating to ensure good heat transfer between the two sides of the plate. The evaporator plate can be in a horizontal or vertical position. Water is allowed to trickle across the face of the lattice structure side of the evaporator plate while a refrigerant gas is flowing through the refrigerant coils. This causes the evaporator plate to be chilled and subsequently causes the water to freeze within the ice cube molds of the lattice structure. The ice making process is complete once the pockets or ice cube molds are full of ice and a solid bridge of ice connects each individual ice cube to form a solid slab with all ice cubes connected. The formation of this solid ice structure is necessary to facilitate the removal of the ice cubes from the evaporator plate or "harvesting" of the ice as it is known in the industry.
Harvesting of the ice is accomplished by reversing the flow of refrigerant gas through the refrigerant coil thereby causing a temporary heating of the evaporator plate and lattice structure. This causes the ice cube "block" described above to unthaw slightly and fall from the evaporator plate. As noted above, the evaporator plate may be positioned in a horizontal or vertical position. The designs which place the evaporator plate in a horizontal position place the ice cube molds on the lower face of the plate and depend on gravity to harvest the ice cubes. Those designs which place the evaporator plate in a vertical position use either a mechanical probe to urge the ice block from the lattice structure or the lower face of the individual ice cubes molds is sloped downwardly to aid gravity in harvesting the ice. It is these designs which use a vertically oriented evaporator plate to which the present invention is directed.
As noted previously, the evaporator plate and lattice structure is constructed from a highly conductive metal such as copper to give superior heat transfer characteristics. The copper base material is then coated with nickel or similar metal to enhance this heat transfer characteristic and provide a smooth, abrasion resistant surface texture. In a new machine this arrangement works quite well. The ice is quickly formed on the evaporator plate during the freezing cycle and then efficiently harvested as described above. Unfortunately, as the cycles of freezing and harvesting ice build, the smooth, abrasion resistant surface becomes worn with rough spots, pits and in some cases the nickel coating completely eroded. This rough surface texture in the individual ice mold pockets causes the ice block to stick or hang in the molds when ice harvesting is attempted. The sticking of the ice slab forces the heating or harvesting cycle to be extended thereby causing increased melting of the individual ice cubes before the slab will loosen and fall from the evaporator plate. The result is partially melted cubes, increased cycle time, and decreased production of ice cube volume.
The current solution to rectify this decreased production problem is to clean the surface of the individual ice molds with a chemical cleaner. This takes considerable time on the part of the technician and gives only a slight increase in ice cube production and is a temporary fix at best. Replacement of the evaporator plate is not a viable solution owing to the method of attachment of the refrigerant coil and the cost involved. The present invention solves these problems in a simple, cost effective manner to allow the ice cube making machine to operate at peak efficiency, thereby providing considerable cost savings to the owner.
2. Description of Related Art
Various types of methods and apparatuses to aid in the formation and harvesting of ice have been shown and used.
U.S. Pat. No. 4,366,679 to L. R. Van Steenburgh, Jr. shows a vertically disposed evaporator plate design which uses a different refrigerant coil design in combination with a mechanical probe to help ice harvesting.
U.S. Pat. No. 4,448,598 to G. LaMonica et al. reveals a system for ice harvesting that uses heating of the evaporator plate with a pneumatic system for separating the ice from the evaporator plate.
U.S. Pat. No. 4,843,827 to J. M. Peppers discloses a vertical evaporator plate design that uses heating of the evaporator plate in combination with a sonic or ultrasonic frequency vibration to assist in ice harvesting.